Steering column assembly

ABSTRACT

A collapsible steering column assembly comprises a telescopic steering shaft that is supported within a steering column shroud, comprising a first shaft having a hollow end, the inner surface of the hollow end being provided with a plurality of inwardly facing elongate splines that each extend axially along the inner surface, and a second shaft that has an end that is located within the hollow end of the first shaft, the second shaft being provided with a set of outwardly facing elongate splines that each extend axially along the outer surface of the end of the second shaft, the splines of the second shaft inter-engaging the splines of the first shaft to prevent relative rotational movement of the two shafts whilst permitting the two shafts to move axially relative to one another at least in the event of a crash. A contact device is located at the end of the second shaft that is located within the hollow end of the first shaft that includes a contact member defining a contact part that contacts the tips of a plurality of the splines of the first portion, thereby to take up any radial free play between the end of the second portion and the first portion at least in the location of the contact device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage of International Application No.PCT/EP2016/067471, filed 21 Jul. 2016, the disclosures of which areincorporated herein by reference in entirety, and which claimed priorityto Great Britain Patent Application No. 1514614.5, filed 17 Aug. 2015,the disclosures of which are incorporated herein by reference inentirety, and European Patent Application No. 15461549.6, filed 27 Jul.2015, the disclosures of which are incorporated herein by reference inentirety.

BACKGROUND OF THE INVENTION

This invention relates to improvements in steering column assemblies.

It is known to provide a collapsible steering column assembly comprisinga steering shaft that is supported within a steering column shroud. Toprevent significant injury to the driver in the event of a crash thesteering column should be able to collapse as an axial load is appliedthrough the steering wheel, for instance in a front impact where anunrestrained driver is thrown onto the steering wheel.

The steering column shaft may collapse through the use of a weakenedsection of shaft. However, in a typical modern vehicle the steeringshaft is able to collapse telescopically with a first part of the shaftsliding over a second part of the shaft. Advantageously, this sametelescopic motion may be used to provide for a range of adjustment ofthe steering column assembly for reach. In that case, the shaft istypically supported within a shroud that is also telescopic andcomprises two portions: an upper shroud portion and a lower shroudportion. A locking mechanism fixes the steering shaft at a desiredlength, and this is arranged typically so that it is overcome in a crashto permit the desired collapse in length.

To allow a torque to be carried across the two parts of the steeringshaft, the end portion of one part of the shaft—typically the uppershaft that is nearest the steering wheel—is hollowed and provided withinwardly extending elongate splines around the circumference of theinner surface. These engage corresponding outwardly facing splines on anend of the other part of the shaft. The splines prevent relativerotation of the two parts of the shaft about their common axis whilstallowing the shafts to slide telescopically. A low friction coating maybe provided on the splines in the form of an overmolding, which also hasthe benefit of allowing the dimensions of the splines to be closelycontrolled. This is important to prevent the two parts of the shafttilting relative to one another.

The present invention aims to at least partially ameliorate problemsassociated with free play present between the two parts of thetelescopic steering shaft in such a steering column assembly.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect the invention provides a collapsiblesteering column assembly comprising a telescopic steering shaft that issupported within a steering column shroud, the telescopic steering shaftcomprising:

A first shaft having a hollow end, the inner surface of the hollow endbeing provided with a plurality of inwardly facing elongate splines thateach extend axially along the inner surface,

a second shaft that has an end that is located within the hollow end ofthe first shaft, the second shaft being provided with a set of outwardlyfacing elongate splines that each extend axially along the outer surfaceof the end of the second shaft, the splines of the second shaftinter-engaging the splines of the first shaft to prevent relativerotational movement of the two shafts whilst permitting the two shaftsto move axially relative to one another at least in the event of acrash,

characterized by further comprising a contact device located at the endof the second shaft that is located within the hollow end of the firstshaft that includes a contact member defining a contact part thatcontacts the tips of a plurality of the splines of the first portion,thereby to take up any radial free play between the end of the secondportion and the first portion at least in the location of the contactdevice.

The applicant has appreciated that there may be some free radial playbetween the two shafts because of the need to allow for some dimensionaltolerances in the manufacture of the shafts. In particular to ensure thesplines do not bind when they are sliding axially it is important tocontrol the tolerances but this is difficult to achieve precisely. Theprovision of the contact device takes up any free radial play betweenthe first and second shaft portions and in doing so may help reduce therisk of the column shaft vibrating during use by altering the naturalfrequency of the shaft and additionally improving the stiffness of theshaft. This may also help prevent a rattle noise being produced from thesteering shaft.

The contact device may comprise a resilient member that is secured tothe second shaft and is placed under a static force, the magnitude ofthe force setting the outer dimension of the member. Where the outeredge of the member forms part of a circle, the force may set thediameter of that circle.

The static force may compress any combination of compression, tension orbending or twisting force that causes the resilient member to deforminto shape that differs from its nature rest shape when no load isapplied. Most preferably the force is a compressive force.

The resilient member preferably comprises an element that is discretefrom the end of the second shaft and is secured to the second shaft by afastener, the fastener applying a force to the resilient member thatcontrols the outer dimension of the element.

In an alternative, the resilient member could be an integral part of thesecond shaft part.

The contact member may comprise a generally truncated conical shape withan inner diameter and an outer diameter that is secured in a firstregion towards the inner diameter to the end of the second shaft portionby a fastener, the member being arranged such that the outer edge of themember define the contact portion that engages the tips of a pluralityof the splines of the first shaft part. The first region may define ahub of the contact member.

The axis of rotation of the member may be coincident with the axis ofrotation of the second shaft part.

The member may be secured to the second shaft part by the fastener suchthat a second region of the member that is radially offset from the hubof the member engages a profiled surface of the end portion of thesecond shaft, whilst the hub is axially offset from the end of thesecond shaft and engages the fastener.

The fastener may be adjustable to vary the force with which the firstregion of the member is pulled towards the end of the second shaft part,whereby as the hub is pulled closer towards the second shaft part theprofiled surface presses on the second region of the member to cause themember to deform, thereby altering the outer radial diameter of theconical member.

The fastener may include a biasing means that acts between a fixed partof the fastener and the hub of the contact member. This may comprise aspring, such as a coil spring.

The contact member may be secured to the end of the second shaft suchthat the cone points away from the second shaft, the profiled surface ofthe end of the second shaft being convex whereby as the fastener drawsthe conical member onto the terminal end the cone splays and increasesin outer diameter.

In an alternative, the truncated conical contact member may be securedso that the cone points towards the second shaft, the terminal endportion of the second shaft being convex, whereby the fastener pulls theconical member into the convex terminal end portion causing the outerdiameter to be reduced.

Where the terminal portion is convex it may be defined by a simplechamfer provided around the end of the second shaft part.

The fastener may comprise a threaded bolt that passes through a hole inthe member to engage a threaded hole in the second shaft. The head ofthe bolt may be provided with a profile suitable for engagement with asuitable tool that allows the bolt to be torqued up. The biasing means,where provided, may comprise a coil spring that is locatedconcentrically around the stem of the bolt.

A single bolt may be provided that engages a threaded hole in the secondshaft. The hole may extend axially along the second shaft and may be onthe axis of rotation of the second shaft.

As an alternative to a bolt, a threaded stud may be secured to the endof the second shaft part that passes through a hole in the dished memberand the dished member secured by a nut.

The thread of the bolt or nut or stud may be provided with a lockingcompound or adhesive to prevent movement once it has been set, typicallyduring initial assembly.

The first shaft part may have a bore that extends along its full lengthto allow access to the adjustable fastener with the second shaft engagedwith the first shaft.

In use, the second shaft part is pushed into the first shaft part andthe adjustable fastener adjusted until the member has taken up anyunwanted free play. The friction may then be checked to ensure theanti-vibration device is not pressed too firmly onto the inwardly facingsplines. This check could alternatively be performed by deliberatelyvibrating the shaft during adjustment of the fastener and noting fromthe change in resonant frequency when the member has just come intocontact with the splines.

The skilled reader will appreciate that the generally truncated conicalmember may have many shapes that can all be considered to be generallyconical. It may only be conical on one surface—the one that engages thesecond shaft part. The outer edge need not be continuous, but shouldextend over at least three regions that are spaced apart by approx. 120degrees to allow the anti-vibration device to self centre the secondshaft part within the hollow end of the first shaft part.

In one preferred arrangement the contact member may comprise a hubportion and a plurality of radially extending fingers or petals thatproject away from the hub portion and form the generally conical shape,the hub defining the radial inner portion whereby the fastener pulls onthe member and the fingers or petals each defining an arcuate outercontact outer portion at the extreme tips of the fingers or petals thatengages the splines of the first shaft portion.

It is preferred that the arcuate edges cover as much of a circular pathas possible, to contact the maximum number of spline tips.

The terminal portion of the second shaft may press upon each finger orpetal in a region approximately midway between the hub and the terminaledge of the petals, each petal acting as an individual leaf spring.

The contact member should be resilient so that as the fastener isloosened the member will move back towards its unstressed shape. It mayfor instance comprise a metal member such as a spring steel member. Butit could be made from a plastically deformable material, accepting thatduring installation the member can be splayed as more tension is appliedbut on releasing tension it will not spring back to the original shape.This makes assembly harder but still possible with care.

There may be at least 5, or at least 6, petals, each having a radialouter surface defining the contact part that follows an arc that lies ona circle centered on the axis of the member and axis of the telescopicshaft.

Providing petals allows each one to independently adjust as the fasteneris adjusted, to give the optimum take up of radial play between the twoshaft parts without introducing excess friction.

The member, or at least the portion that engages the splines of thehollow end of the first shaft, may be of a low friction material such asa plastic material. For example, a polietylen material may be used. Aswell as optimally being a low friction material the material shouldpreferably be hard wearing so that it is not worn away during adjustmentof the length of the steering column shaft.

The first shaft portion may comprise an upper portion of the steeringcolumn assembly and may be located closer to the steering wheel than thesecond shaft portion. The end of the first shaft portion may be providedwith a plurality of external splines for engaging splines of a steeringwheel hub.

The lower shroud portion may comprise an input shaft for a torquesensor.

The torque sensor may additionally comprise an output shaft connected tothe input shaft by a torsion bar. The output shaft may form an input toa gearbox assembly.

The shroud may also be telescopic and may comprise an upper shroudportion and a lower shroud portion, the two being able to movetelescopically to vary the length of the shroud.

The upper shroud portion may be located towards the end of the steeringshaft that is nearest the steering wheel and the lower portion may belocated towards the end of the shaft furthest from the steering wheel,the upper portion being at least partially received within the lowerportion so that the upper portion can telescopically collapse into thelower portion during a crash.

The shroud may be secured to the vehicle by a support bracket thatincludes two support bracket arms that depend from a base portion toembrace the shroud,

a clamp rail that is releasably secured to the upper shroud portion, theclamp rail including a slot that extends generally horizontally,

a clamp pin that extends through an opening in each of the arms of thebracket and through the generally horizontal slot in the rail, the clamppin carrying a clamp mechanism that is movable between an unclampedposition in which the rail can move freely relative to the clamp pin anda clamped position in which the rail is fixed relative to the clamp pin.

The steering column assembly may be of fixed length, telescopicallycollapsing only in the event of a crash, or may be adjustable for reach,or adjustable for rake, or adjustable for both reach and rake.

The invention may, in a second aspect comprise a method of assembly of asteering column assembly according to the first aspect comprising thestep of adjusting the force applied to the contact member to remove anyradial free play between the contact member and the first shaft.

The method may comprise setting the force to precisely set the outerdiameter of the contact member to that required to remove any radialplay, or to a diameter slightly larger than this yet ensuring that thereis not an excessive friction force between the contact member and firstshaft.

The step of adjusting may be performed after the end of the second shaftis inserted into the hollow end of the first shaft.

The step of adjusting may comprise tightening or loosening a bolt thatcomprises part of the contact device.

Other advantages of this invention will become apparent to those skilledin the art from the following detailed description of the preferredembodiments, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of an exemplary steering column assemblyaccording to the present invention;

FIG. 2 is an enlarged view of the region of the assembly of FIG. 1 wherethe two shafts forming the telescopic steering shaft are engaged;

FIG. 3 is view (a) in plan and (b) in cross section along the line A-Aof the member of the contact device of the assembly of FIG. 1; and

FIG. 4 is a view of a part of a second embodiment of a steering columnassembly showing the location of an alternative contact device on theend of the second shaft.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a collapsible steering column assembly 100 comprisesa two part telescopic steering shaft that is supported within a steeringcolumn shroud. The shroud has an upper part 101, that is located closestto a steering wheel (not shown) and a lower part 102 that is locatedfurthest from the steering wheel and secured in the example to a housingof a gearbox for a gearbox 107. The shroud supports the steering shaftwhich comprises a first (upper) shaft 103 that is closest to thesteering wheel and terminates with a splined coupling for receiving ahub of the steering wheel. The end of the first shaft 103 that isfurthest from the steering wheel is hollowed out, and the inner surfaceof the hollow end is provided with a plurality of inwardly facingelongate splines 103 a that each extend axially along the inner surface.Each spline has the same height from root to tip, the tips all lying ona circular path that is centered on the axis of the first shaft 103.

The steering shaft also comprises a second shaft 104 that has an endthat is located within the hollow end of the first shaft 103, the end ofthe second shaft being provided with a set of outwardly facing elongatesplines 104 a that each extend axially along the outer surface of theend of the second shaft. The splines 104 a of the second shaftcomplement and interengage with the splines 103 a of the first shaft toprevent relative rotational movement of the two shaft portions whilstpermitting the two shaft portions to move axially relative to oneanother at least in the event of a crash or during adjustment for reach.

Secured to the end of the second shaft 104, within the hollow end of thefirst shaft part, is a contact device. The contact device, which mayfunction as an anti-vibration device to reduce vibration induced rattleof the two parts of the steering shaft, occupies a space between thesecond shaft and the inside of the hollow portion of the first shaft103, making contact with the tips of the splines 103 a of the firstshaft part and helping to prevent excess vibration of the steering shaftby modifying the resonant frequency of the two part shaft. To do this,the spacer device must ensure there is no gap between the contact deviceand the inwardly facing splines, and ideally the contact device appliesa very light pressure onto a plurality of the splines around thecircumference of the hollow end portion with zero free play so that noradial movement of the second shaft relative to the first shaft ispossible in the region where the spacer device is located.

The contact device in the example shown in the drawings can be seen mostclearly in FIG. 2. The device comprises a resiliently deformable member108 having a radially outermost edge 113 that lies at a constant radiusfrom the axis of the second shaft so that all parts of the outer edgelie on the desired circular path. The contact member 108 is secured tothe end of the second shaft by a bolt 109. This is shown more clearly inFIG. 2 of the drawings. The contact device has a generally truncatedconical shape with an inner diameter and an outer diameter. Morespecifically, the member comprises a hub portion 112 and a plurality ofradially extending fingers or petals 114 that project away from the hubportion and form the generally conical shape. Six petals are shown, theouter edge of each petal lying on the circular path and forming a set ofsix arcs, each spanning about 50 degrees of the circular path. Theregions between the petals are cut away right back to the hub of theresilient member. The petals 114 define the cone shape.

The resilient contact member 108 is fixed onto the end of the secondshaft part by the fastener. This comprises a bolt with a threaded stem109 and a head 109 a. The stem passes through a hole in the hub of themember that is smaller than the head 109 a of the bolt (the bolt beingon the opposite side of the member to the second shaft) and the stem isengaged into a complimentary thread of a threaded hole in the secondshaft. The head 109 a of the bolt is provided with a profile suitablefor engagement with a suitable tool that allows the bolt to be torquedup.

The bolt holds the contact member such that the hub 112 of the member isslightly stood off from the end of the second portion and the head ofthe fastener pulls the inner portion towards the second shaft 104. Thethreaded stem of the bolt is therefore placed under tension as thepetals of the member 108 are forced into contact with the second shaftpart. Each petals 114 acts as a leaf spring and is deformed by thiscontact, causing the outer edge of the petals 114 to splay outwards. Theamount of tension in the stem 109 of the bolt determines how much theresilient member is splayed and this sets the diameter of the circularpath on which the outer edge of the petals lies. The region of thesecond shaft 104 that contacts the petals 114 in this example ischamfered, ensuring the petals 114 can slide smoothly over the end ofthe second shaft as the screw is tightened. The chamfer 116 in effectdefines a cone shape that complements the cone shape of the contactmember, the cone formed by the second shaft being forced into the coneof the contact member by the bolt.

In use the bolt is tightened or loosened to deform the petals 114 untila condition is reached in which the diameter of the arcs defined by theouter edge of the contact member is perfectly in contact with no freeplay with the inner tips of the splines 103 a of the first shaft. Thishelps to lower the resonant frequency of the overall shaft compared withan arrangement without the anti-vibration device, especially where thereis only a short overlap of the splines. The screw can be set once duringassembly and testing and then left during the life of the steeringcolumn assembly. An adhesive applied to the threads of the shaft ensuresthat the screw cannot work loose over time.

In an alternative arrangement of contact device, which is shown in FIG.4, a biasing means 220 in the form of a coil spring, may be located onthe threaded stem 209 of a fastener bolt that acts between the head 211of the bolt and the hub of the contact member 208. The spring is set sothat it is compressed. The spring applies a compressive force onto thecontact member, pushing it firmly onto the chamfered end of the shaftpart 204, so that the force is dependent on the set position of the boltand also the amount of compression of the coil spring 220. The contactmember 208 is the same in this embodiment as the one shown for the firstembodiment, and the bolt may also be the same albeit that the head isset further from the end of the second shaft 204. Of course, toaccommodate the spring a longer bolt may be required compared with thatuse in the first embodiment.

This alternative arrangement ensure that even if the outer edge of thecontact member 208 becomes worn during operation, the spring willcompensate this effect by always ensuring the contact member is pressedonto the tips of the teeth in the hollow end of the first shaft. Thespring will continue to take up wear until either: (a) the hub of thecontact member hits the end of the second shaft, (b) the spring becomesuncompressed or (c) the remaining compressive force in the spring isinsufficient to apply the required bending force to the petals of thecontact member.

When such a spring 220 is present there is no need to tighten the boltafter column assembly. It can be set on exactly specified distance whichensures correct spring tension before column will be assembled and inthe next step on the assembly line column can be assembly. The contactmember petals will deform a little bit along with the coil spring toallow the contact member to deform and fit perfectly into the hollow endof the first steering shaft.

In accordance with the provisions of the patent statutes, the principleand mode of operation of this invention have been explained andillustrated in its preferred embodiments. However, it must be understoodthat this invention may be practiced otherwise than as specificallyexplained and illustrated without departing from its spirit or scope.

The invention claimed is:
 1. A collapsible steering column assemblycomprising a telescopic steering shaft that is supported within asteering column shroud, the telescopic steering shaft comprising: afirst shaft having a hollow end, an inner surface of the hollow endbeing provided with a plurality of inwardly facing elongate splines thateach extend axially along the inner surface, a second shaft that has anend that is located within the hollow end of the first shaft, the secondshaft being provided with a set of outwardly facing elongate splinesthat each extend axially along an outer surface of the end of the secondshaft, the splines of the second shaft inter-engaging the splines of thefirst shaft to prevent relative rotational movement of the two shaftswhilst permitting the two shafts to move axially relative to one anotherat least in the event of a crash, and further comprising a contactdevice located at the end of the second shaft that is located within thehollow end of the first shaft that includes a resilient contact memberthat contacts tips of a plurality of the splines of the first shaft,thereby to take up any radial free play between the end of the secondshaft and the first shaft at least in the location of the contactdevice, wherein the resilient contact member is secured to the secondshaft and is placed under a static force, a magnitude of the staticforce setting an outer dimension of the resilient contact member.
 2. Thecollapsible steering column assembly according to claim 1 in which theresilient contact member comprises an element that is discrete from theend of the second shaft and is secured to the second shaft by afastener, the fastener applying a force to the resilient contact memberthat controls the outer dimension of the element.
 3. The collapsiblesteering column assembly according to claim 2 in which the fastenerincludes a biasing means that acts between a fixed part of the fastenerand the hub of the resilient contact member.
 4. The collapsible steeringcolumn assembly according to claim 3 in which the biasing meanscomprises a coil spring.
 5. The collapsible steering column assemblyaccording to claim 2 in which the resilient contact member comprises ahub portion and a plurality of radially extending fingers or petals thatproject away from the hub portion and form the generally conical shape,the hub defining a radial inner portion whereby the fastener pulls onthe resilient contact member and the fingers or petals each defining anarcuate outer contact outer portion at the extreme tips of the fingersor petals that engages the splines of the first shaft portion.
 6. Thecollapsible steering column assembly according to claim 1 in which theresilient contact member comprises a generally truncated conical shapewith an inner diameter and an outer diameter that is secured in a firstregion towards the inner diameter to the end of the second shaft by afastener, the resilient contact member being arranged such that an outeredge of the resilient contact member defines the contact part thatengages the tips of the plurality of the splines of the first shaft andthe first region defines a hub of the resilient contact member.
 7. Thecollapsible steering column assembly according to claim 6 in which theresilient contact member is secured to the second shaft by the fastenersuch that a second region of the resilient contact member that isradially offset from the hub of the resilient contact member engages aprofiled surface of the end of the second shaft, whilst the hub isaxially offset from the end of the second shaft and engages thefastener.
 8. The collapsible steering column assembly according to claim7 in which the fastener is adjustable to vary a force with which thefirst region of the resilient contact member is pulled towards the endof the second shaft, whereby as the hub is pulled closer towards thesecond shaft the profiled surface presses on the second region of theresilient contact member to cause the resilient contact member todeform, thereby altering an outer radial diameter of the conical shapeof the resilient contact member.
 9. The collapsible steering columnassembly according to claim 1 in which the resilient contact member, orat least the portion that engages the splines of the hollow end of thefirst shaft, is of a low friction material.